In order to reduce as much as possible the release of debris into geostationary orbit and make available slots in such a busy orbit for new satellites, it is recommended that a geostationary satellite at the end of its life, before complete exhaustion of its propellant, should be transferred to a supersynchronous graveyard orbit that does not intersect the geostationary orbit.
The effectiveness of such a re-orbiting maneuver depends totally on the precision in the calculation of the propellant residual which will be used for the maneuver. An under evaluation of the residual will make the successful completion of the maneuver not possible and an overestimation will cause a reduction in the operative time for the spacecraft, with a consequent loss of money for a commercial spacecraft.